There is proposed a rotation detection apparatus to detect the rotation of a gear-shaped rotor, e.g., in Patent Literature 1. More specifically, the proposed rotation detection apparatus includes a plurality of magnetoresistive elements and a processing circuit. The processing circuit processes the output of each magnetoresistive element. Each magnetoresistive element configures a first magnetoresistive element pair and a second magnetoresistive element pair that are disposed to face the rotor and electrically form a half-bridge circuit.
The midpoint potential of each magnetoresistive element pair changes based on each tooth of the rotor. Thus, the processing circuit compares a differential output of the midpoint potential of each magnetoresistive element pair against a threshold value and generates a binarized signal by binarizing the differential output.